D&D 5E (2014) Hero’s of the Borderlands unboxing, spoilers.

[THEMNGMNT]

I'm not clear how leveling works here. Is this milestone or XP? It does feel like, between the wilderness and Caves of Chaos booklets, characters might end up hitting level 4 before all is said and done.

Per the adventure, after the PCs clear 2 caves, they level up to 2nd. After they clear 3 more caves, they level up to 3rd. I believe there are 11 caves in total (plus Wilderness encounters) so clearly they're meant to spend the majority of the adventure at 3rd level.